Depolymebizatiqn



- P t nted Mar. 8, 2,1 I

UNITED STATES PATENTS OFFICE 2,110,409 p 1 DEPOLYMEBIZATION or 1mm YPOLYACETALS Wallace 11. Carothers, Wilmington, hara si or to E. I. du ,Pont de Nemours a Company, Wilmington, Del., a corporation of Delaware No Drawing. Application January 2. 1935, Se-

rial No. 179. In Canada November 25, 1932 v 10 Claims. This invention relates to' new compositions of matter, and particularlylto new cyclic acetals and other products obtained thru the depolymerization of linear polyacetals.

: It is to be noted that the word in chemical literature and also in the description ofvthe present invention in three senses: in as a generic expression which represents the compound derived from the carbonyl grouping such 10 as is present in aldehydes and ketones by replacmay be represented by the following equations; 10 ing the carbonyl oxygen with two OR groups in which R and R. represent hydrogen or a (the R. of the two ORgroups may be one and the simple or substituted hydrocarbon radical such same group in which case a cyclic compound is as an allgyl, aryl, aralkyl or' alicyclic radical, and formed); (2) as a subgenericexpression repre- R represents .a hydrocarbon radical such as an 5 senting the acetals formed from acetaldehyde; alkyl, aryLaralkyl, or alicyclic radical:

(3) as-a specific expression to represent the defl- H nite chemical individual, diethyl acetal, i. e., the diethyl ether of ethylidfiie glycol. The com- HOOHOH'OH+R C K 'E pounds wherein the carbonyl oxygen is replaced glycol aldehyde R by one hydroxyl and one OR group are called I R! RI 20 hemiacetals; X Y cylic acetal This case is a contin'uation in part of copending application Serial No. 548,701, filed'July 3, 1931. 2. HOOHIOH10H+ c OOHICH20+2ROH Cyclicacetals as a broad class are not new. 4 \QR Hill and Hibbert (J. Am. Chem. Soc. 45, 3117, U 3124 (1923)) prepared a number of cyclic'acetals f 2 33.? R by reacting polyhydroxy compounds, e; g., ethylcyclic metal I ene glycol, with either acetylene or acetaldehyde. When these methods are pp e to yc0 More recently Hallonquist and Hibbert (Can. J. o 'hlgher glycols (h e in the Sense that the Research 8, 129 (1933)) prepared a number-of ydrO y S are Sep t frOm each other y a cyclic acetals by the interchange method. This chain of r h 5 a o other atoms), the

method consists in heating the glycol with an products are not cyclic acetals but linear conopen chains monomeric acetal whereupon the densation polymers. The reaction,.using an open lowerboiling alcohol distills over, leaving the dechain acetal (interchange method), may be repsired acetal. The c m n p p y these resented by the following equation, in which R 35 authors were limited to cyclic acetals containing and 2 have the same meaning-as inthe above 5, 6, and 7-membered rings. The method is inf rm l represents the number f reacting applicable to the preparation of cyclic acetals molecules of glycol and Metal, and n fepresemsr containing more than 7 members in the ring; in an integer greater than our: I

40 fact, the method gives peor yields when applied B1 on 40 to the preparation of the. 'I-membered rings.

When these methods are applied to higher glycols (glycols in which the hydroxyl groups are R! on separated by a chain of at least 5 atoms), linear glycol open m mm 5 polyacetals are formed as shown in 'copending apg i serial 7 filed even date mommies-maniac +0105).

A cyclic hemiacetal seems to have been prepared in poor yield by Helferich and 'Schaier (Ber. 57, 11mmpolymm who;

1911 (1924)) by treating'hydmxynongldehyde The reaction follows thesame course when an 50 with methanol and hydrogen chloride. The prealdehyde i used in place of the Op chain a etal sumable product of this is the methyl lactolide but is more m t carry out as is disclosed in the copending application Serial No. 178, filed ocrmcmncnocm Y of even date herewith. Even when n is 4, Reac- This is a IO-membered ring but contains only one I "acetals is used oxygen atom in the ring/ It is essentially a methyl ether of a cyclic hemiacetal.

U. S. Patent 1,837,273 discloses the preparation of certain cyclic acetals by heating an aromatic aldehyde with analiphatic glycol; The pat-c ented products do not have the large rings characteristic of those of the present invention.

v The above reactionsfor the formation of cyclic acetals containing 7 or less members in the ring tion 3- predominates.

I oflering only the possibility of Serial No. 657,408, filed if r has issued" as D. 8. Patent 2,020,298 and also compounds. Both glycols andacetals (or aide-4 hydes) may be regarded as bifunctional compounds and may react in two. ways: Two mole.- cules may wndense with the formation of a cyclic compound (Reactions 1 and 2), or many molecules may condense by a chain mechanism to form a linear condensation polymer (Reaction 3). with compounds presenting the possibility of rings of less than 7 members, Reaction 1 or 2 occurs almost exclusively; with compounds capable' of giving 7-memhered rings, both types of reaction take place, whereas with compounds higher membered rings,R.'eaction 3 occurs practically exclusively.

This invention has as an object the depoly merization of linear polyacetals with the forma'-. tion of ldepolymerization products. A further obiect of the invention is the preparation of cyclic acetals containing at least 8 annular members, at least two of which are oxygen. A further ob iect is the preparation of odoriierous compounds useful in the perfume and analogous arts. ,A still further object is thepolymerization of the monomeric depolyrnerization products of polyacetals. Other objects will appear hereinafter.

These objects are accomplished by the following invention wherein depolymerization of linear condensation products of acetals to form lower molecular weight depolymerization products including monomeric-and dimeric polyacetalshaving at least 8 annular members of which atleast two are oxygen, and hydroxyalkyl vinyl ethers, is carried out by exposing the linear polyacetal to a suitable elevated temperature under 'a suitable pressure, preferably a reduced'pres- Theprocess for-the depolymerization of suitable linear polyacetals tocyclic acetals of at least 8 ring members, atleast two of which are omgen, is similar to that described by Hill and Carothers (J. Am. Chem Soc. 55, 5031 (1933))" for the preparation of cyclicesters by the depolymerization of linearpolyesters. A suitable method consists in heating the linear polyacetal to a moderately elevated temperature,. e. g., 150- 300 C. in a vessel evacuated to. a low pressure (less than 2.0 mm. of mercury and preferably less than 0.1 mm.) the vessel being provided with a condenseror cooled surface placed very close- (less than 5 cm.) to the surface of the heated acetal. An apparatus of this type is known as a molecular still. [Suitable examples'of such apparatus are shown in copendi'ng application February 18, 1933 which at J. Am. Chem. sec. 54, 1558 (1932). This. treating gives adistillate'consisting of monoamounts of distillate and residual superpolymer formed vary greatly with different polyacetals. These differences are indicated in a qualitative way in Table I for the various acetals. It is to be noted that all the polyaccta'ls prepared from tetramethylene glycol, including the formals,

isobutyrals, and benzals, are easily depolymerized,

giving good yields of-monomeric products and smaller amounts of residual superpolymers. The depolymerization'does not require the 'use of a molecular still; simple distillation at atmospheric pressure may be used. The linear polyacetalsderived from glypols, higher than 1,4 show wide differences in their 'depolymerization behavior.

depending upon the aldehyde or ketone (or monomeric open chain acetal) from which they are derived. Thus,. polyformals' are depolymerized with considerable difliculty. polybenzals some- .what more readily, and the isobutyrals rather easily. In general, the more easily a polyacetal is decomposed the greater the amount of dis-" tillate (depolymerizate), and the smaller the amount of residual superpolymer.

There 'is also a .diflerence ii the nature of the distillate (depolymerizate) obtained from the'various linear polyacetals. The distillate derived from polytetramethylene formal and polytriethylene glycol formal are cyclic monodepending upon the particular "polyacetal and ,upon experimental conditions. The polyisobutyrals from 1,5 and higher glycols, give a monomeric distillate which appears to contain but littlecyclic acetal,'but to consist largely of a hydroxyalkyl substituted vinyl ether of the general formula HO(CH:) OCH=C(CHJ) 2.

The polyacetals derived from acetaldehyde, propionaldehyde, butyraldehv'de, and heptaldehyde give monomeric distillates similar to those derived from the polyisobutyrals.

On the basis of the results obtained with the various polyacetals mentioned in the preceding paragraph (complete list in'Table I), it may be stated that cyclic acetals- (either monomers or dimers) are obtained from the depolymerization of polyacetals in which the aldehyde represented has no replaceable hydrogen on the carbon atom is concerned with the distillate or depolymerizate,

- meric and dimeric p o ind leaves a i alpha to the carbonyl group, i. e., an aldehyde '(superpolymer) ofhi gher molecular weight than having no CH group ammtfto the carbonyl the 011311131 Wlyacem- The present invention group. Formaldehyde, and benzaldehyde are representative of this class. -Aldehydes having pending application serial a replaceable hydrogen" atom on the alpha car- Which has issued 84971352 med of evenbon such-as acetaldehyde, isobutyraldehyde, etc.,

date herewith, -is concerned with the residual superpolymer. 'Iheheatinfi is preferably done in thepresence'of .a catalyst such as camphorsulfonic acid. The molecular still is a preferred but not absolutely necessary form oi apparatus.

From the foregoing discussion it may 'be seen thatthe reaction wherein the macrocyclicacetals (cyclic acetals of at least. 8 annular memgiven inTables II and-III indicate the depoly- -merizate oi the polyformals and the polybenrals to be the cyclic monomersand dimers. The

dimers are odorless, crystalline solids; the monomers possess fragrant odors. The macrocyclic acetals show a tendency to polymerize when heated in the presence" of a trace of p-toluenesulfonic acid.

The monomeric depolymerizate obtained from polyisobutyrals and similar poLvwetals are characterized as hydroxy alhl substituted vinyl no on, .ocn=o by their ready hydrolysis by dilute acids to the corresponding glycol and aldehyde-a characteristic of vinyl ethers, their reaction with phenylisocyanate, and their polymerization when treated with catalysts oi the type used for polymerizing vinyl ethers, the polymerization takingplace at room temperature with catalysts suchas stannic chloride and iodine. The product obtained from the depolymerization of poly-' hexamethylene isohutyral givesacetone on oxidation with potassium permanganate in accordance with the unsaturated ether structure. The

. physical and analytical data and the molecular refractions give further'evidence of the unsaturated ether structure.

The monomeric products (both the cyclic acetals and the unsaturated ethers) obtained from the depolymerization of the linear acetals are'in general mobile liquids, distillable under vacuum, and having fragrant odors. 'Ihe-eyclic monomer obtained from triethylene glycol formal has a fragrant odor remarkably similar to that of triethyleneglyeol carbonate. The monomeric products obtainedYrom the'linear polymers of tetramethylene formal and isobutyral have strong characteristic odors; that of the latter being reminiscent of camphor, menthol, and

eucalyptol.

More complete data concerning thephysical properties of the depolymerization products, of the linear polyacetals are given in Tables I and 11;. Analytic data arerecorded in Table III.

Tamar: I,

Poluacetals and their depolymchzatizm products Depolymerizate Ease of de y- Pdmm merizat on N o. of I Nature I Structure ato I i in ring I Tetramethylene formal Ve easy c Monomer, a liquid .1.-. 7 Pentamethylene form Di cult Dimer, M. P. 45-52 O. and monomer 16 Hemmethylene formal Very diflicu1t- Dimer, M. P. 7l72 O. andtrace monomer--. l8 Nonamethylene formal..- -.do..---. Dimer, M. P. (til-69 G. and trace monomer--. 24 Decamethy-lene f Dimer, M. P. 93-94" C. and trace monomer-.. 26 Tetradecamethylene formal. Dimer, M. P. 103.5l04 C. and trace monomer- 34 Octadecamethylene formal b 'Iriethylene glycol formal. Monomer, M. P. l8 20 C Oyclic---- 11 Hemmethylene acetal-... Probably monomer liquid Open chain Decamethylene acetal .Elexamethylene propional. l Open chain .Hexamethylene n-butyral. i o Ietramethylene isobutyral. Cyclic- Pentamethylene isobutyral. Easy Open chain Hexamethylene isobuty do Nonamethylene isobutyral do 6 o Decamothylene lsobutyral do Hexamethylene heptal.... do -..do Hexamethylene ketal..--. Poor d- I Tetramethylene henzal Monomer liquid .Cyclio--.. 7 Hexamcthylene benzal Dimer, MuP. 122-124 C. and monomer 18 Decamethylene henzal Dimer, M. P. 134-435" C. and I 26 a The term monomer.' signifies that the iproduetiias the molecular weight and empirical formula ot a monomer;

it does not necessarily imply that the product I: The depolymerizate was not characterized c Monomers distilled without the application of vacuum.

4 These polymers decomposed to aconsiderable extent during an acetal structure. I I

attempts to depolymerize them.

. Team .11

Physical pr p rties 0! dcpolumerizates o! poluacetals Polymer (source) Nature of product -$g:g Egg M. P 11', d}

- Caled. Found 'letrameihfilene formal Cyclic monomer- Acetal" 7 nil-117 5 4310 1.0022. 3.38. 26.34 Pentament lene formal 1 o 8 40- 44/l1 l. 4200 Pept'smeth no formal.. Cyclic dimer ro 16 46- 62 gexamethylene formal. n r o iii 71- 72 om thylene formal dn r n 24 as- 60 Decameihylene fonnal. (in r n 26 93- 04 '1 eoamethylene formal. do ro 34 lot-104 Trinthylene glycol formal Cyclic monomer o ll 18- m" Hexamethylene ah.-. Open chain monomer... Ether...-. 60/0. 5 Hexainethylene pr io --...do. K (in 77- 79l3 I 4.. Kflflmethylene n-but'yra do-.. 86%! 1.4646 0.0036 ch00 61.69 Tetramethylene isohutyral. Cyclic monomer Aqetal--... 7 64- 69/19 l. 4385 0.932! 40. 2! 40.18 Peutamethylene isobutyral Open chain monomer... Ether.-.-. 1112-1739/22 1.4500 0.0066 46.47 47.37 Hexanzethylene isobutyral. r n r o 96. 5"}2 l. 4560 0. 9016 51.09 iii. 59 Nonamethylene lsobuty c n r o li7-l22/l l. 4685 0. 8012 64. 94 05. t8 Decnmethyione isobntyral c o. I o l4ll1 I Hexsmethylene heptal. o I o 1%[1359/1 'ietramethylene benzal Cyclic monomer Aeet-al-...- 7 1 l Hemmethyiene benzal Cyclic dimer. o....... 18 121-124 Decamethylene benzal- ...-.rl 26 134-135 The M crystallized in flat needles bf M. P 71-72 C.

Tsau m and purposes of the invention, the following examples are given for purposes of illustration, but not in limitation:

Example 1. -Hezam'ethulene formal a Claisen flask by means ol a metal bath. Distillation of butyl alcohol set in at 155- C. The temperature was gradually raised during 1 hours to 200, C. A current of CO: was passed thru the melt during the last'half hour. The residue was further heated under the vacuum ofan oil pump at'200-210 C. .for 1 /2 hours.

uct (linear polyacetal) was a viscous brown syrup which did not solidify.

Five grams of the aboye syrupy polymer was placed in a 250 cc. modified molecular. still and heated tor-16 hours at 24515 C. under 2 mm. K About 0.2 g. of moist crystalline deposit of a strong mintyodor collected on the condenser; This odor was very similar to that of the dc v polymerizate obtained from hexamethylen'e carbonate under similar circumstances. The distillate was filtered and the crystalline material recrystallized from 70% methyl alcohol. It

andwas the cyclic dimer. The residue was super- .polymeric in character.

I Example 2'.-D cmethvlcne formal 0.1- g. oi FeCla was added, ebullition set in at 165 C. The temperature was elevated to 200 C.

. in three hours. C01.was passed through the melt the last hali hour. Heating was continued under vacuum f for l 'hours at 150---200" C. Thirty-six and five-tenths cc. of alcohol dis.

tilled (theory 37 cc.).' The residue (linear poly- H, 12.1%; mol.

Analysis Probable m comma rm Polymer (source) Nature oi mm flu ma in. c H n. C H n.

Tetrsmethylene iormai Cyclic monomer- Aes tel... 7 B0. 82 0. I) 102 00. 06 0. mil!) Pelitslnethylene iormal. do- 8 02. 07 10. 34 01. 07 10. 70

(10---- 10 02.07 10.34 232 61.70 10.46 m Henmethylene i0 ...d0--.. 18 04.0 10.8 200 04.0 10.6 206307 Nonsmethylene lormal.- do 24 Q. 77 11.- 02 344 I. 11. be 333% (10.... H 70.0 11.0 372 70-8 12.1 850; ....do '.d0. 34 74.4 12.4 484' 74.4 .115 :03 Cyclic monomerdo. 11 01. 86 8. 64 102 31. 00 8. 37 1013 Open chain mono- Ether-.. 00. 07 11. 11 '07. 04 10. 77

Heumethylene propional... 08. 35 ll. 30 168 6. 12 11. I) 440336 Henmethylene n-butyral (D. 70 11. 62 172 70. I! 11.06 171:1 'letrsmethylene isobutyrsl-.- 00. 67 11. 11 144' M. 04 11. as 1442142 Pentamethylene isebutyral. a '0 08. 36 i1. 30 09. 1s '10. 07 Kexamethylene isobutyralour. 10 11.- ea in as. s: 11. as Nonamethylene isobutyrsL- 72. 00 12. 214 73. 43 1a 27 Deumethylene isobutyml. do- 73. U 12. 29 74. 80 11.07 Hexameihylene heptal; do 72. 00 13. 15 73. I) 11. is Tetrsmethylene benzsl. Cyclic monomer- 74. 16 7,. so 73. 34 7. 7! Hexamethylene benssl- Cyclic dimer 76. 72 8. 74 75. 74 8. 86 Decsrnethylene do .1. 77. 80 9. 92 77. 34 0. 70

Sample had polymerired se ne priorto analysis. 7 Having outlined above the general principles hot 'ethyl acetate, treated with decolorizing carbon, and allowed to crystallize. The compound separated as a crystallinepowder in spherulites and melted at 565-57 C. It was dried to constant weight in vacuum at 100 C. and analysed (C, 58.9; H, 11.7; mol. wt., 2190). Itis soluble in chloroform, benzene, carbon tetrachloride, and xylene: insoluble in'alcohol, ether, petroleum hydrocarbons and acetone.

Eight grains of the crude material was placed in a 250 cc. modified molecular still and heated at. 230-250 C.-i'or 48 hours. The slightly moist distillate (2 g.) had a pleasant, rather eamphoraceous odor. Alter crystallisation it melted at 93-94 C. It was the cyclic dimer.

lzomple 3.Tetrudecamethylene formal f Thirteen and two tenths'grams oi tetradecamethylene glycol and 10 g. of dibutyl iormal were heated together in the usual way with leCl: as catalyst. The waxy product (linear polyacetal) was dissolved. in hot ethyl acetate and treated with decolorizing carbon. On cooling, the solution deposited the polymer in the form of a microcrystalline powder. -It was driedin a vacuum at 100 C. for hours and analysed (C, 73.1%; wt. cryoscopicslly in bensene,

Five grams oi the crude polymer was placed in a modified molecular still and heated, for

hours. Three grams of slightly pasty distillate with a rather muskyodor collected Recrystab. lized from alcohol, it was odorless and melted at 103.5-104' C. It was the cyclic dimer. The residue was superpolymeric in character.

Erample 4 .Triethulene glycol formal ,Seventy-five grams of triethylene glycol, 84 g.

of dlbutyl formal; and 0.12 g. of camphorsulfonic' acid were heated together by means of a metal bath at 150-190 C. for 2 hours. Nitrogen was blown thru the mixture the last hour; 89 cc.

' of butyl alcohol (theory91 cc.) distilled. The

residue (linear polyacetal), a. viscous syrup, was heated at 200-250 C. for 3 hours; 57 g. of partially crystalline distillate collected. Most of a this was lost by polymerization on attempting toredistil it. The experiment was repeated and a sample purified for analysis, by fractional crystallization. The product-melted at 18-20 C; and was the cyclic monomer. I It had a mild fragrance 4 much like that of triethylene glycol carbonate.

When it was heated for 1 hour at 100 C. with a trace of camphorsulfonic acid it polymerized to a viscous syrup. When boiled with dilute hydrochloric acid it evolved formaldehyde.

Example 5.-'-Hezb emyzene pr m' naz i ether, washed with aqueous sodiumcarbonate and water, and the'residue fractionally distilled at 3 mm.; 11.5 g. came over at 775-79" It wasmonomeric in character and its-prop rties indicate it to be the unsaturated ether,-

HOCHz (CH2), 4CH2OCH=CHCH3. v

It polymerized to a viscous syrup when heated at 100 C. with a trace of camphorsulfonic acid.

. Example 6.He:ramethy le1 e isobutyral Seventy and. eighttenths grams of hexamethylene glycol, 127.2 g. of dlbutyl isobutyral,and

0.1g. of pure p-toluenesulfonic acid were heated together at 160- 200 C. for hours with blowing with nitrogen during the last hour; "110 cc. of butylalcohol distilled (theory 110, cc.). The'residue, the linear polyacetal, was a somewhat viscous light orangeliquid- A sample was removed, dissolved in ether, washed with aqueous sodium carbonate and water, dried with potassium carbonate, and recovered by evaporation of the ether. After-drying it was analyzed. Calcd. for. CioHzuOa :C,69.'76%;' H,11.62%; mol. wt. 1'72.

'scopically'in benaene) 7'12; 705 l The remainder was heated at 1 mm. at 150-190 .C. and, 'withtheexeepti on of 3 g. of dark, viscous residue, distilled. The distillate was dissolved in ether, washed with sodium-carbonate and water,

dried, and fractionated. The main fraction, 50

d g.,' distilled at 96.5 cat 2 mm There was four The main fraction (monograms of residue.

meric) was the unsaturated ether.

nocmkcnh icrhocn=c (CH3) 2. I Ezagnple 7.-Nonamethylene isobutyral' Linear polynpnamethylene isobutyral was pre-' pared in a manner analogous to that usediwith hexamethylene' isobutyral. 0n depolymeriza-.

tion, it yielded a monomeric product boiling at l 5 11'7-122 C./1 mm. Its p perties have the structure nocmigmiicmocnwwmh;

It had-a viscosity of 0.22 poise (bubble tube) which did not change in one i hour's heating at 98 -100 0. A trace of p toluene'sulfonic acid introduced and heating continued one hour at the same temperature. The viscosity ofthe cooled liquid was 8 'poises. Further heating did not change this value;

Ezample 8.-He:rainethylene Twenty-nine and five-tenths grams of hen.- methylene glycol, 64 grams of dibutyl heptal, and 0.1 gram of camphorsulfonicacid were heated together in the usual way, first at atmospheric pressure, then with blowing, and finally in 'a vacuum.v The theoretical quantity of alcohol dis-* tilled during the first two operations and 45 grams of semisolid distillate of B. P. 120-170 C./1 mm. in the last. The liquid was separated, washed with dilute NazCOa and dried. It was then distilled at 1 mm. The largest fraction, 9

grams, distilled at 129-1'35 C. It was yellow and had a very faint pleasant odor. Its properties indicate it to be monomeric in character.

Emmfiple 9.He:camethylene Icetal" Eighteen and eight-tenths grams of -dibutyl ketal, 11.8 g. ofhex'amethylene glycol, and 0.05 g. of camphorsulfonicacid were heated together at 145-1'70 C. bath temperature for 40 minutes with blowing with nitrogen during the last 5 minutes.

Practically the theoretical quantity of. butyl alcohor distilled. The syrupy residue (linear poly-. ketal) was then heated at, 5 mm. pressure up to 210 0. bath temperature. Twelve and fivetenths g. of yellow distillate, mostly crystalline, distilling at 92-130'C. was collected. Thecrystalline material, amounting to 9 g., wasseparated and identified as liexamethylene glycol. The filtrate; which possessed a mild floralfrag rance, crystallized partially on standing.

Example 10 .Tetra methyiene benzal 125-140 C. for 30 minutes with blowing with Initrbgen during the .last 10 minutes. Ninetyfour per cent of the theoretical amount of methyl indicate it to Twenty three and six-tenths g. of tetramethyl- Y :ene glycol, 31.9 g. of dimethyl benzalpand 0.1 g. of camphorsulfonic acid were heated together at alcohol'distille'd; The residue was heated .under 2 mm. pressure and 41 g. of distillate (B. P.

99 --100 C.) was collected. The distillate consisted of two phases andhad a strong odor of tetrahydrofurane. It was. diluted with ether,

washed with dilute Na2co3, dried with K2003 and recovered by evaporating the ether. Distil lation under.12 mm. yielded two main fractions 'of 10 'g. each with boiling points of 123-127" C./12 mm. and 121-1215 c./12 mm. The sec- 0nd was analyzed and was found to be the cyclic monomer. It had a pleasant odor, reminiscent ofbenzaldehyde.

Example 11.l'iezamethyle1 e benzal \Thirty-seven and seven-tenths 3. 01 hexa methylene glycol, 50 g. of" dimethyl benzal; and 0.1 g. of camphorsulfonic acid were heated tor gether in the usual way for 30 vminutes at ll5-160 C'. with blowing with nitrogen at the end; (The dimethyl benzal "was prepared according to Voss (Ann. 48 5, 283 (1931) from di- .1 net,hyl sulflte, benzaldehyde, and methyl alcohol.) Methyl alcohol distilled (86% oi theory). The residue (linear polyacetal) was heated under 2 mm. for one hour at 170-220 C. ,Very little distilled. The residual polymeric product consistedof 62 g. of a light yellow. very syrup of faint benzaldehyde odor.

- Nine g. of polymer wererplaced in a smallmolecular still heated by the vapors of alphachlorodiphenyl, B. 1?. 268 C. and heated for 7 hours under 0.5 mm. Five and five-tenths I. of semi-solid distillate collected. The solid 'phase was filtered and, after two crystallizations from .falcohol, gave needles which melted at 122-121 C. lt was the cyclic dimer.

The filtrate was dissolved in ether, washed with dilute NazCO: and dilute NaHSQudt'iBd:

over KzCOs, and recovered by distillation. of the ether. It was. then put in a small modified molecular still fitted with a drip cup and heated one hour up to 90 C. maximum. 1 Five drops of distillate collected. It was a mobile liquid with a pleasant odor resembling benzaldehyde and was the cyclic monomer. Anal. Calcd. for CuHnOz:

C, 75.72%; H, 8.74%. l'bilnd: C, 75.80%; H.

I The residue increased-in viscosity during the distillation and finally resembled the original polymer. Anal. 'Calcd. for (com-om: C,

75.72%; H, 8.74%. F0und:-C, 73.78%; H, 8.73%.

Emmple .1Z.--Decamethulene benzat Twenty-six grams of decamethylene glycol, 24

g. dimethyl benzal, and 0.06 g. oi camphorsuli'onic acid .were heated together as in the previous at low temperature.

' preparation. Eighty-three'pe'r cent oi the theoretical amount of methyl alcohol distilledu' The product, obtained in almost theoretical yield, was

depolymerlzation products) listed below, including for comparison a few simple cyclic acetals prepared by the usual method (glycol plus aldehyde) were sealed in tubes (5.5 mm. inside diameter) to v a depth 01' 6.5 cm. with a 4.5 cm. air space above the surface. The tubesin which the tormals were polymerized were 4 mm. in diameter (inside? filled to a depth of 6 cm. with a'3.5 cm. air

space above the liquid. Two tubes were made ofevery compound, one tolbe kept pure as a blank, the other catalyzed by the addition oi a thin fiake otf camphorsullonic acid about 1 mm. square. The times oi. flow of the liquids on inversion of the tubes we're measured at the outset and at the end of each period of heating. The tubes were always allowed to stand at 25 C. for several hours before the measurements were made. The

catalysed samples were heated with results as hour; 8 secxafter 5% hours} 5 sec. after 6% hours; 12.5 see: after 11% hours at 100' C. and 1 hour at 150 C.; 12.0 sec. after 11% hours at 100C- and 3 hours at 150 C. I

Monomeric depolvmerisation product of polypentamethulene "isobutvral a pale yellow, very'viscous syrup with little odor.

Nine and five-tenths grams was heated for 12 hours at 230-240 C. in a modified molecular still fitted with adrip cup. About 7 cc.-distilled. Two-tenths gram of a solid phase was removed and recrystallized iromalcohol. It separated as needles and melted at 134-135 ,C. It was the cyclic dimer. i

The liquid distillate was diluted with benzene washed with dilute NaHSO: and NaiCOs, dried withKaCO': and recovered by distilling the solvent up to 100 C. bath temperature. About 1 cc. came over before the liquid residue, originally quite mobile, became very viscous and distillation ceased. The distillate had a mild pleasant odor, not unlike benzaldehyde. -'lhe ready polymerizabllity of the residue and the analysis of the distillate indicate it to be impure monomer. Anal. Calcd. for CrIHssOs: C, 77.86%; H, 9.92%. Found: vc, 75.59%; x, 12.06%.

,The monomeric depolymerisation products or.

linearpolyacetals, which linear polyacetals have a unit length oi atle'ast silht atoms, may be polymerized by heating, preferably in the presence c! s polymerisation catslyst such as camphorsulionic acid. The following example indicates the polymerization oi the monomeric depolymerilation products of linear of unitlengthofatleasts'. Depolymerisationploductiofpolyacet'als'otunitlengthlessthanaare included for purposes of comparison:

. Iasmple 13.Polmtioa ol M a mot ine rolnccloh Samplesot various mm (mm uric 2.2 sec. at start; 5.0 sec.after 1 hour at 100 C.; 135 sec. after 2 hours at 100' C.; l min. sec.- after 4 hours at 100 C.; l min. 21 sec.- atter 8 hours at 100 c.

Monomeric depolumerization hezamethyleneisobuturai Distillation was carried out in.a fiat type Hickman molecular still at 0.5 mm.

2.0.sec. at start; 26 see. after 15 min. at 100' C.; 50 sec.; after 2% hours at 100 C.; 2 'min,-30 sec. aiter 8% hours at 100 C.; 8 min. sec. after l3% hours at 100? C.; almost immobile after 17% hours at 100C.

[Monomeric depolumerizatm product of poly-- nonamethylene isobutwraL-See Example 7.

Trime'thulene formal (cyclic acetal with 6- .membered ring) .4.5 sec. at start; no change after 2 hours at 100 C. and then 1% hours at Tctramcthulene formal (cyclic acetal with 7- membered ring) .4.5 sec. at start; no e P oduct of poly after 2 hours at C.; 35 see. after 2 hours at 100 C. and 30 min. at C.; almost immobile after 2 hours at 100 C., and lwhours at 150' C. Pentomeflwlene formal (cyclic acetal with 6- memberedring) .4.5 sec. at start; 13 see. after 2 hours at. 100' C.; 16 see. after 2 hours at 100' C., and 30min. at 150 C416 see. after 2 hours at 100 C and 1% hours at 150 C.

Tetramethflene bonsai (cyclic acetal with 'lring).4 .5 sec. start: 30sec. alter 15 100 sec...a!ter 4 hours at'roomtemperature; did not incresseon is not limited to the use of the polyacetals cited in the foregoing tables and examples. Polyacetals may be derived from other glycols, for

example, diethylene glycol, heptamethylene glyoctamethylene glycol,

col, dipropylene glycol, alpha-'methylpentamethylene glycol, octadec'amethylene glycol, dodecamethylene glycol, tridecamethylene glycol, 1,3-xylylene alcohol, 1,4- xylylene alcohol, etc. The aldehydes restricted to those present in the polyacetals mentioned in the examples. As examples of other 'aldehydes and ketones which may be used,

thefollowlng are mentioned: propionaldehydep phenyiacetaldehyde, trimethylactaidehyde, anisic aldehyde, methyl ethyl ketone, cyclohexa-' none, acetophenone, etc. The cyclic acetalsderived from the 1-5 glycols or higher are as a class new products not obtainable by methods heretofore employed.

The new cyclic acetals of the present invention may be represented by the formula wherein R and Ft are hydrogen or monovalent tertiary hydrocarbon radicals and R is a divalent organic radicai; and preferably a divalent hydrocarbon; having at least 5 annular atoms between the two oxygen atoms. I

. Ferric chloride; p-toluenesulfonic acid, and

camphorsulfo'nic acid have been mentioned as catalysts for the preparation and depolymerization of the polyacetals. Other halides, e. g., stannic chloride, antimony chloride, aluminum chloride,,boron trifluoride, and hydrogen chloride itself may be employed as well as other sulfonic acids,such as benzenesulfonic acid, xylenesulfonic acid, etc. Acidic compounds in general function as catalysts. Thus, magnesium sulfate and potassium acid sulfataare .useful. Itis desirable however, to select a catalyst "which is mild in its action. and does not cause excessive darkening o'r decomposition. The sulfonic acids are particu-' .larly suitable. With, 'an acetal of acidic proper ties, such as a chloro acetal, itisoften-unnecessary to add a catalyst in the preparation of the polyacetal. In the depolymerizalglonof the polyacetal, a catalyst is likewise oftenunnecessary.

The conditions for the depolymerization of the linear polyacetals may be varied. While the use of a molecularstill for this transformation is in many cases preferable, an inert,gas or organic yapor may be passed thru the molten linear poly-.

mer with or without the use of reduced pressure to carry away the volatile products; The reaction may also be carried out in a solvent with I or without the addition of catalysts with arrange- (CO) group is attached only to carbon atoms.

mentsfor distilling. and returning the solvent after separating, the volatile products of the reaction distilling with it. In certain cases the process may be'effected by using powerfully adsorbent materials, such as silica gel, adsorbent carbon, activated alumina, etc., to 'bring about theirreversible adsorption of the volatile reaction products. The reaction may be carried out at a temperature high enough to make the rate of (or 'ketones), represented in the polyacetals are not reaction appreciable but low enough to avoid any thermal decomposition. The use of temperatures over 300'. C. is not advisable.- In many cases the linear polyacetals can be depolymerized by conventional distillation methods; this is true for the polyisobutyrals mentioned in Table I. The depolymerization of certain polyacetals may start at temperatures as low as 90 C.

The cyclic monomersmay be polymerized under varying conditions. Polymerization may be carried out between 75' and 200 C. for extended periods.- Catalysts such as camphorsulfonic, benzenesulionic, p-tolu'enesulfonic, and other ,sultonic-acids, aluminum'chloride, stannic chloride arc of advantage. The polymerization may also be' carried'out in solution altho in general more slowly. Interpolymerization rwith other heat polymerizablematerials may be eifective. The polymers may be used in coating, impregnating, adhesive, etc.,compositions.

The open chain monomers maybe polymerized at temperatures ranging from room temperature (circa 25 C.) up to approximately 200 C. Peroxides, stannic chloride, aluminum chloride, iodine, etc., catalyze the reaction which may also be carried out in solution in ordinary solvents.

Interpolymerization with vinyl esters,--methacryl'ic esters,.-unsaturated ketones, etc., may be effected. The polymers may be used in coating,

impregnating, adhesive, etc., compositions.

The process of the present invention affords a method for the synthesis of macrocylic acetals which cannot be prepared by. any other method thus far developed. These compounds generally have fragrant odors rendering them useful in the preparation of perfumesi Through the selection of the proper polyacetal, the process of the present invention aifords a method for synthesizing hydroxyalkyl substituted vinyl ethers. The

substituted yinyl ethers are formed in a liquidphase reaction which is simpler than the. vapor phasereaction for the preparation of substituted vinyl ethers from linear monomeric acetals as described in the literature. The vinyl ethers may be converted into resins useful as adhesives, im-

Cir

pregnating agents, and incoating compositions and plastics.

Where the statement is made with respect to an atom A that it is falpha to another atom B,

it is meant that A and B are directly joined to each other. Where the atom A is beta to B it is attached directly to an atom which is in turn attached directly to B.

The above description and examples are inwithin the scope of the claims.

I claim: 1.,A-dimeric cyclic acetal of a glycol having a chain of five to eighteen atoms between the hydroxyls, with an aldehyde of the formula R CHO.

wherein R is selected from the class consisting of hydrogen and monovalenthydrocarbon radicals wherein the carbon attached to the carbonyl 2. Cyclic triethylene glycol formal. 3. A cyclic acetalof the formula ir -ch a wherein R is selected from the class consisting,

of hydrogen and monovalent hydrocarbon radicals wherein the carbon attached to the acetal grouping is attached onlyto carbon atoms and wherein each R is a divalent organic radical having a chain oi the to eighteen atoms between the acetal oxygens. V

4. kcyclic acetal of the formula,

lu-crr R1 atom in the beta position to the i v o 7 carbon is carbon, R. isselected from the class consistingof hydrogen and monovalent hydrocarbon radicals and R is a divalent organic radiacetal cal having a chain of five to eighteen atoms between the acetal omens and is selected from the class consisting of divalent open chain hydrocarbon radicals, xylylene radicals, and divalent radicals consisting. of a plurality of divalent open chain hydrocarbon radicals joined through ether oxygen.

g 5. Cyclic benzals of the formula oan-ca" a a r wherein R is a divalent organic radical having a chain oi live to eighteen atoms between the acetal oxygens.

6. Cyclic benzals of the tormu la wherein R is a divalent organic radical having a chain of 5 to 18 atoms between the acetal oxygens and is selected from the class consisting of 'divalent open chain hydrocarbon radicals, xylylene radicals and divalent open chain radicals consisting oi a plurality of divalent open chain hydrocarbon radicals joinedthrough ether oxygen.

and purifying the depolymerization product.

7. Cyclic'iormals oi the formula nc a A 0 6 in the beta position to the carbon is carbon, RF is selected from the clam consisting of hydrogen and monovalent hydrocarbon radicals and R is a divalent organic radical having a chain 01' live to eighteen atoms be- 15 tween the acetal oxygens and is selected irom the class consisting of divalent open chain hydro carbon radicals, xylylene radicals, and divalent radicals consisting of a plurality of divalent'open chain hydrocarbon radicals ;oined through ether 90 oxygen. i

' 8. Cyclic iormals of the formula '2 4.7 wherein R is a divalent open chain radical consisting 01 a plurality of divalent open chain hydrocarbon radicals Joined through ether oxygen.

9. Process for the preparation oi cyclic acetals oithe formula J wherein each atom acetal wherein each atom beta to the m ocarbon is carbon, R" is selected irom the class consisting of hydrogen and monovalent hydrocarbon radicals and R is a divalent organic radical having a. chain of five to eighteen atoms be- 45 tween the acetal oxygens, which comprises depolymerizing the corresponding linear polyacetal by heating the same at low pressure and isolating 10. The process of claim 9 wherein a sulfonic acid catalyst is used. N n WALLACE H. CARO'IHIRS- 

